Homo naledi: an anti-climax

In September 2015 a barrage of publicity announced the remarkable unearthing of the remains of 15 diminutive hominins, dubbed Homo nadeli, from the floor sediments of an almost inaccessible South African cave, part of the equally hyped ‘Cradle of Humankind’ UNESCO World Heritage Site near Johannesburg. An international team of lithe women speleo-archaeologists was recruited for the excavation, for which the original discoverers were incapably burly. The remains included numerous examples of still articulated intricate bones, such as those of feet and hands, and none show signs of dismemberment by large scavengers. Indeed the discovery chamber was so far from the cave entrance that such animals probably were unaware of their presence. These features and the sheer complexity of the system strongly suggested that cadavers had been deliberately taken to the chamber; implying that the deep penetration had been accomplished using fire-brand illumination. What seized the headlines was the possibility of ritual burial, although sanitary disposal or panicked refuge from predators seem equally, if not more likely.

Now yet more fossils have been reported from a separate chamber at a crawling distance about 150 m away from the original but closer to the system’s main entrance (~85 m). These add at least other 3 individuals to the H. nadeli association, with sufficient similarity to indicate that all 18 belong to H. naledi. This wealth of detail enabled the team of authors (Hawks, J. and 37 others 2017. New fossil remains of Homo naledi from the Lesedi Chamber, South Africa. eLife, v. 6, online; http://dx.doi.org/10.7554/eLife.24232) to perform a detailed comparative anatomic analysis of the species. The results are a mosaic, showing some post-cranial affinities with australopithecines, H. habilis, H.floresiensis, H. erectus, Neanderthals and anatomically modern humans, and others, such as the hands and shoulders, that are not well matched with other hominins. Their crania show a similar broad spectrum of resemblances, and as regards dentition they are distinctly primitive. They are also on the small-brained side of the hominin clade. Despite the astonishing abundance of fossil material, not a single artifact was found in the cave system, despite the apparent similarity of its hands to those of ourselves and Neanderthals.

With plenty of scope for speculation, H. nadeli remains enigmatic. The big question looming over the 2015 announcement of the species was its age, the discovers suggesting about 2 Ma, and placing on the direct line of human descent. On the same day as the fossil description there appeared a multi-method dating analysis (Dirks, P.H.G.M. and 19 others 2017. eLife, v. 6, online; http://dx.doi.org/10.7554/eLife.24231.001), which showed that with little doubt that the H. nadeli association was deposited between 236 ka and 335 ka; around the time when anatomically modern humans first emerged and stone tools had undergone a >2 Ma technological evolution. To me, the only sensible conclusion at present is that H. nadeli is another addition to the 6 species living and in some cases coexisting across the late Pleistocene world, and that expansion of ideas beyond that must await DNA analysis; a definite possibility considering the age of the fossils, their seemingly good preservation in a relatively dry cave system and the new possibility of cave soils as well as bones yielding genetic materials. The leader of the research team, Lee Berger of the University of the Witwatersrand now maintains, together with four other members of the research team, that H. nadeli may be a coelacanth-like survivor of Homo’s earliest diversification and that ‘we cannot exclude that this lineage was responsible for the production of Acheulean or Middle Stone Age tool industries’.

I’m sure it will come as no surprise to you either that I and a great many others don’t agree with everything that you say about H Naledi. The remains of several were discovered in chambers deep within a cave system and show no sign of disaggregation that would be expected from water transport. The deliberate burial idea is neither easily disproven nor proven and is a possible explanation of the odd nature of the remains and their context Moreover, there are obvious differences from modern bonobos. I’ll leave it at that but would welcome comments on this from other readers.

Thank a lot for your reply, Steve. I know & understand your objections.
My interpretation is based on comparative biology, not on geology. Biologically, there’s nothing uniquely-human in naledi: naledi’s humanlike traits (esp.the humanlike feet) are not human-derived, but primitive-hominid, e.g. prenatal chimps have humanlike feet with the great toe pointing forward: “Only as it approaches its birth does its foot acquire the appearance of a hand. At no stage of its development does the human foot resemble that of an adult ape” (C.Coon “The Story of Man” p.12).
Of course, AFAIK there’s no evidence of water transport at naledi’s site according to prof.Dirks (pers.comm.). Naledi fossilized in stagnant water (mud-stone), i.e. wetlands or forest swamps, where lowland gorillas & bonobos (still) wade sometimes bipedally for aquatic herbaceous vegetation (AHV, google “bonobo wading” & “gorilla bai”), but it’s comparative biology (curved manual phalanges, full plantigrady, iliac flaring etc.) that shows that this is where naledi lived most of its time, not the open savanna.
In any case, not only prof.Berger’s supposed naledi’s “distance running” & “tool making” but most of all his “deliberate burial” idea are far-fetched anthropocentrisms. We find fossil accumulations of several A.afarensis individuals (so-called “First family”) e.g. in Hadar, Afar Locality 333: “Generally, the sediments represent lacustrine, lake margin, and associated fluvial deposits related to an extensive lake that periodically filled the entire basin” (Johanson cs 1982), “The bones were found in swale-like features … it is very likely that they died and partially rotted at or very near this site … this group of hominids was buried in streamside gallery woodland” (Radosevich cs 1992) – they say “group of hominids”, but later it was realized this fossilization happened over a long time, not by sudden water transport. BTW, Lucy A.L.288 also lay in a “small, slow moving stream … Fossil preservation at this locality is excellent, remains of delicate items such as crocodile and turtle eggs and crab claws being found” (Johanson & Taieb 1976), and this is the case for most if not all australopithecines: Pliocene australopiths “existed in fairly wooded, well-watered regions” & Pleistocene robust australopiths “in similar environs and also in more open regions, but always in habitats that include wetlands” (Reed 1997). So the discovery naledi in caves underneath the former wetlands is not unexpected. Most (earlier) S.African australopiths are found in such caves: IMO they simply died where they lived, just like their afarensis cousins in E.Africa.
The undoubted “obvious differences with bonobos” (esp. full plantigrady, smaller front teeth, dental wear) are most parsimoniously explained by naledi’s dwelling in wetlands more than extant bonobos do, please google “Pan naledi 2017 Verhaegen”.
I think it’s time paleo-anthropology gets rid of the old savanna-running interpretations of human evolution, and also of the idea that australopithecines are human ancestors (because “bipedal”) to the exclusion of Pan & Gorilla. Most likely, chimps & gorillas also had more bipedal ancestors, not for running over savannas, but simply for wading bipedally in swamp forest & wetlands (AHV) like bonobos & lowwland gorilla still do. This implies that many if not all australopith fossils might be more closely related to Pan or Gorilla than to Homo (hypothesis of prof.Kleindienst & many others independently, see my Hum.Evol.papers).
Best wishes & thanks –marc

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